Ultrafiltration, size exclusion chromatography, and ethanol trituration have concentrated anti-HIV activity of sponge extract in a high molecular weight fraction whose 13C-NMR and elemental analyses are consistent with a sulfated 6-deoxy-polysaccharide. The same approach has led to similar results with an aqueous extract of tunicate. The trituration/13C-NMR analysis approach is proving to be a useful confirmation for the chemical characterization/-dereplication protocol's indication of sulfated polysaccharides.